Objective: This study longitudinally evaluated whether parent-ratings and self-ratings of executive function (EF) predicted the academic and overall functioning of college students with ADHD and whether EF deficits mediated the relationship between ADHD symptoms and functioning. Method: A prospective longitudinal study of 59 college students comprehensively diagnosed with ADHD and their parents who completed ratings at the beginning and end of the school year. Results: Student-rated motivation and parent-rated emotion regulation significantly predicted overall impairment above and beyond symptoms of ADHD. Student-rated EF motivation mediated the relationship between ADHD symptoms and overall impairment. Student-rated EF organization mediated the relationship between ADHD symptoms and end of the year grades. Conclusion: Motivation and organization aspects of EF appear particularly important for functioning. However, given the study’s modest sample size, additional longitudinal research is needed to confirm these findings and to develop best-practice assessment and treatment recommendations for college students with ADHD.